Neuromagnetism, the study of induced and spontaneous magnetic fields of the human brain, has been shown experimentally to provide a non-invasive technique that allows precise spatial localization of several sources which could not be well localized by measuring surface potentials. Important applications of this technique include the localization of epileptogenic foci, studies of evoked sensory response and, more recently, research on cognitive processing. Neuromagnetism has promise of becoming a new imaging modality to show dynamic brain function, as opposed to CT and NMR which show structure, and PET which gives only the time averaged activity level. With the instrument improvements addressed herein, a decrease in the time, expense and risk required for epileptic patient evaluation is predicted. An estimated 25,000 to 100,000 patients in the USA might benefit from neurosurgical resection and, if neuromagnetometry becomes a routine procedure capable of localizing epileptogenic foci, the number of operations could increase dramatically from the present few hundred per year. For clinical viability, a number of instrument improvements are required; the most critical of these is reduced instrument noise. Currently, environmental magnetic noise, intrinsic system noise, and "brain" noise in the subject are all problems, and the measurement times necessary for adequate signal averaging (up to a few days for some patients) are too long for the technique to be clinically viable. The Phase I objective is to identify, measure and develop techniques to reduce the contribution of all significant noise sources in order to obtain an overall system noise below 20 ft/[Hz], a value which allows reasonable averaging times. Specific tasks include: development of hardware and software to electronically improve rejection of ambient fields, field gradients, and field derivatives; development of an improved line frequency comb filter; development of improved rf shielding; installation of a lower noise SQUID sensor; reduction of other intrinsic noise sources; and analysis of the potential reduction of brain noise obtainable by using a multi-channel array. Other instrument improvements will be addressed in Phase II. This proposal is in response to the D.H.H.S. S.B.I.R. solicitation and is applicable to several research areas described therein: 1) the convulsive, developmental and neuromuscular disorders program, and the fundamental neurosciences program of NINCDS, 2) the biotechnology program of DRR, 3) the brain imaging program of NIMH and, 4) less directly to programs in NIA, NEI, and NICHD addressing behavior, learning, cognitive processing, and visual processing.